Control arrangement for level rolling metal plates and sheets in reversible rolling mills



April 4,

Filed Oct.

J. NEUMANN AND SHEETS IN REVERSIBLE ROLLING MILLS 2 Sheets-Sheet 1 K.CONTROL ARRANGEMENT FOR LEVEL ROLLING METAL PLATES April 4, 1967 K. J.NEUMANN 3,312,092 ATEs CONTROL ARRANGEMENT FOR LEVEL ROLLING METAL PLAND SHEETS IN REVERSIBLE ROLLING MILLS l 2 Sheets-Sheet 2 Filed Oct. 25,1963 United States Patent Olce 3,312,092 Patented Apr. 4, 1967 3,312,092CONTROL ARRANGEMENT FR LEVEL RULLING METAL PLATES AND SHEETS ENREVERSIBLE ROLLING MiLLS Karl Josef Neumann, St. Ingbert, Saar, Germany,assignor to Verwaltungsgesellschaft Moeller und Neumann OttoneHandelsgesellschaft Filed Oct. 25, 1963, Ser. No. 318,984 Claimspriority, application Great Britain, Oct. 25, 1962, 40,399/62 13 Claims.(Cl. 72-13) The invention relates to a control -arrangement for levelrolling metal plates and sheets, and more particularly to a controlarrangement in which the rolling action produces a correct overall flowof the rolled material to provide a level surface and an even thicknessof the plates and sheets.

A correct ow control in rolling metal sheets is particularly importantin the final passes so as to prevent that the rollers exert varyingpressures either in the center or along the edges because of the rollerdeflection due to the rolling pressure. In a correct ow controlledrolling operation the sheet ows, i.e. is stretched or pressed uniformlyover its entire width.

It is in the nature of the product, namely the at metal sheet, thatduring rolling between dat rolle-rs the sheet has a tendency not to comeout straight with respect to the mill. The sheets are thus rolled byconducting them centrally of the groove caused by the deflection of thework rollers. The metal sheet has thus a greater thickness at the centerthan at the edges. For this reason it is necessary to apply smalle-rrolling pressures during the nal passes in order that the rollerdeliection becomes smaller and to have a metal sheet which comes out ofthe last pass with surfaces which are as much as possible parallel toeach other. Even in the linal pass some deflection of the smooth rollerswill occur so that even in the case of hot rolled metal sheets there isalways a greater thickness in the center than along the edges, even ifit is only a few hund-reds of a millimeter.

In the last series of passes it is therefore necessary to consider,-aside from adjusting the amount of reduction to be rolled, also theneed for a lower pressure in order to carry out the `final pass with apredetermined rolling pressure at which the roller deflection,considering a certain camber in the grinding of the rollers, wouldproduce only a very small guide groove. For this reason it has been thepractice for the operator to set the reduction during the final seriesof passes with decreasing values according toa previously determinedpass schedule, but largely according to his own judgment in theexpectation that with this reduction the rolling pressure would alsodrop. But this is not always the result, considering for example thecase where between two passes an extended pause may occur during whichthe rolled material cools down. Consequently the material would have ahigher specific deformation resistance so that in spite of a decreasedreduction relative to the previous pass, the rolling pressurepredetermines the roller deflection and the formation of the groove isthe same or larger than in the previous pass. Only experience and goodjudgment ot the operator can produce a good result with the operatingmethods practiced hitherto.

A particular difficulty resides in the fact that the rolling pressureshould not drop linearly in a uniform manner, but that it should droprelatively more during the rst passes of the last series of passes, andless during the nal pass because t-he rolling action takes place only inthat case with a correct ow control and without the formation of folds.It is practically impossible for the operator to correctly observe thecurve according to which the rolling pressure should drop merely byactuating the adjusting device, thus by reducing the passes.

Accordingly it is an object of the invention to make the liow controlledrolling independent of the experience or judgment of the operator bymeans of -a novel electronic control arrangement.

Control arrangements are already known in which during the rollingoperation the rolling pressure, the thickness of the reciprocating metalsheet and the Width of the sheet are measured and -are used as basis forthe pass reduction in the subsequent passes, wherein the values arederived during the rolling operation from sample sheets and merely servefor the subsequent controlled rolling of the sheets having the samedimensions and of the same quality steel. The meaning of the term passreduction `as herein employed signifies the amount by which thethickness of the rolled sheet is reduced with each pass, as indicated inFIGURE 1 at Ah. But it is known that in mills for rolling coarse stockvarying end thicknesses are often rolled from one sheet to the next. Itis therefore another object of the invention to derive from themeasurement values of an existing guide pass the pass reduction for thesubsequent pass of the same sheet according to a predetermined rollingpressure schedule.

The contr-ol arrangement of the invention includes also the continuouslyincreasing deformation resistance of the sheet during cooling so that inthe calculated pass reduction also the cooling during operation stoppagebetween two passes is taken into consideration.

Instead of introducing the decreasing rolling pressure according to apredetermined rolling pressure schedule, the control arrangement of thisinvention proposes to determine the rolling pressure by introducing thewidth of the sheet according to a predetermined schedule of the rollerdellections which decrease toward the last pass, wherein the passreductions are pre-calculated for the passes which follow the guidepass, and whereby a check is made to see if the sum of the passreductions corresponds to the diterence between the crosssectional sheetthickness so measured in the guide pass and the desired nal thickness snof the sheet.

In case of a deviation the pre-calculation is to be repeated with `adilerent characteristic of roller deflection or a di'erent number ofpasses in the last series of passes until the difference so-sncorrespond-s to the sum oi the pass reductions.

The invention comprises also a method of operating the novel controlarrangement according to which the precalculation of the last series ofpasses is repeated with each pass of this series while decreasing theset number of passes. j

The invention is described hereafter by way of examples, but withoutlimitation thereto, in conjunction with the accompanying drawingsshowing the control arrangeient in the form of block diagrams and inwhich:

FIG. l shows a rolling process and illustrates clearly the significanceof the symbols employed in the formulas given in this description;

FlG. 2 shows a block diagram of a control arrangement for determiningthe pass reduction of the passes following a guide pass based on apredetermined rolling pressure; and

FlG. 3 shows a block diagram of the same control arrangement forcalculating a pass series after the introduction of the characteristicsof the desired course of the roller deflection.

The mathematical basis for the control arrangement of the invention isthe so-called Eckelund formula In this formula Pw is the rollingpressure. The value d is the so-c-alled pressed length which may be seenlrom FIG. 1 land depends on the roller diameter d and he reduction Ahaccording to the formula given here. lhe sheet width b is also variable,even when the rolling )poration is started with the slabs having thesame dimenions, because during the first passes not only longitudii-allypressing passes are carried out, but after turning the lab by 90transversely pressing passes are also made, o that the width isA notalways the same lat the beginning )f the final pass series. The value Kwis the specific deormation resistance of the work material and depends)n the thickness s of the work material, the rolling speed v tnd thework material temperature t. It is equal to the um of the existingspecific deformation 'resistances KS :inuence of the outlet thickness sof the work material),

(v (influence of the work material speed v) and Kt (in- Y luence of therolled material temperature t). The course f the values of the existingspecific deformation resist- Luces as functions of s, v and t isobtained from known yalues. The values increase with the increase of the'olling speed and with the reduction of the outlet thickless s andtemperature t. We have thus:

From FIGURE l we obtain for a subsequent reverse )ass additionallyso-sl-:Alz

The control diagram illustrated in FIGURE 2 is deigned for the purposeof determiningj `at the beginning if the nal pass series in which adecreasing rolling pres- `ure speed w is applied, the values Pw, Ab andb by measirements and to derive therefrom the specific deformaionresistance KW of the particular sheet. Conversely he reduction A111 :ofthe sheet for the subsequent pass is :alculated from the probableKw-value for the subsequent )ass yand from the predetermined rollingpressure over he pressed length Id. The Width of the rolled material b'emains the same because in this instance no widening )asses are carriedout.

The operation of the control arrangement illustrated s as follows:

The frame 1 of the reversible mill is `provided with the iressure gaugebox 2 for measuring the rolling pressure W. Thickness measuring devices3 and 4 are mounted )n both sides of the frame and in each case only theneasuring device which lies behind the frame in the rollng directionwill feed its value into line 17. This is obained by `alternatelyconnectible contacts 5 and 6 in ines 7 and 8. In the case illustrated,in which the sheet s rolled from left to right, contact 6 is closed andconact 5 is opened, so that only the measured value of the hicknessgauge 4 is relayed as absolute value. In `a :omparison device 9 thedifference Aho between the measlrement values of the thickness gaugedevices 3 and 4 is )btained, which is introduced over line 9a and closed:ontact 9b into a calculator 12. A width gauge 10 which s illustratedonly schematically and which operates ap- Jropriately by a photoelectricscanning of the sheet edges, nay be l`disposed `on either side of theframe, and furnish :ontinuously measurement values, as the sheet widthdoes 1ot change for several passes upon starting the control for:arrying out the last pass series. After a speed increase )f the rollersthe rolling speed v is taken from the num- )er of revolutions of therollers and is calculated and ndicated in device 11.

The effect of the control is the following: The derived 'eduction Abofrom comparison device 9 enters calculator l2 into which the rollerdiameter d is also fed from the adjusting device 13. In calculator 12the pressed length do is calculated according to the formula indicatedabove 1nd fed to calculator 14. The sheet width b from meas- 1ringdevice 10 and the existing rolling pressure PW(J from y)fessure gaugebox 2 are also fed to this calculator. The

specific deformation resistance KW of the just worked sheet iscalculated from these values according to the formula indicated and isfed to a device 15. A function element 16 is associated with calculator15 and the outlet strength sc from the thickness measuring device isintroduced into this element over line 17. It furnishes the existingdeformation resistance Ks depending on the sheet outlet thickness s0according to the function Ks), which is introduced into the deviceaccording to known values. In the device 15 Ks is deducted from KW sothat at rest the two existing values Kv-l-Kt are obtained. This sum is'conducted further into the device 13 in which the existing deformationresistance KV based on the rolling speed is deducted. Kv is furnished bythe function device 19` into which the rolling speed Vo passes over line20 and into which the dependence value Kv=f(v) is fed.

From device 18 the rest value Kt goes into the function element 21 intowhich the dependence Kt=f(t) is fed so that the work materialtemperature t is eliminated at the outlet and may be read on theindicator 22. In this respect the calculator system is employed also todetermine the actual temperature of the work material.

From this point on all the calculations are directed to determiningthrough the kW-value which is correct and changed for the subsequentpass and through a smaller rolling pressure a new redu-ction Ahl. Thekw-value changes due to cooling of the metal sheet which depends on thetime t between the two passes and the sheet thickness s.

After a measurement value for temperature t is available the sameinstruments may be employed for the reverse calculation in a secondcalculating operation only when the flow of the first calculatingoperation in the direction described so far is interrupted. While thesheet is still being worked this is obtained by actuating a solenoid 23for the contacts 5, 6, 9b, 24 and 32 in such a manner that the lines 8for the value s, 9b for Aho, 25 for the value PW 4and 32 for the value Vare interrupted without closing line 7 of gauge 3. But some values mustbe retained or stored for the reverse calculation such as the sheetwidth b in device 26, temperature t in device 27 and the initialthickness s in device 28. The measured temperature to of the guide sheetis fed into calculator 29 which in reference to the time and themeasured sO-value feeds a continuously decreasing temperature value t1into the calculator 21, The time factor is introduced by a timing device30 into the calculator 29 while the value s0 is introduced throughdevice 28. The value so remains constant until the beginning of thefollowing pass, thus until a new measurement value which must come fromthe gauge 3.

The continuously decreasing temperature value furnishes in device 21 anew higher Kt-value which is fed into device 18 For the following pass agreater rolling speed V1 is employed which is set at the adjustingdevice 21 and fed into the function device 19. This device furnishes anew and increased Kv-value which is processed in device 18 and forms atthe outlet a new value Kv-l-Kt fed to the calculator 15. Since in thefirst calculating pass a new sheet thickness s is not yet available,rather the original Ks-value is present, a Kw1-value is fed fromcalculator 15 into device 14 which value is corrected only in view ofthe decreasing temperature and the increased rolling speed.

With the new value Kw1 a new ldl value is calculated in device 14 fromthe available sheet width b from device 26 and from the pre-selecteddecreased rolling pressure PW from the adjusting device 33. The device12 derives now from the introduced value ldl a new reduction Abl.However, this value cannot be correct yet because the existingdeformation resistance KS has not been changed yet. In order to obtain aprovisional new outlet thickness s1 for the following ipass A111 is fedto a calculator 34 into which through a line 35 also the outletthickness so retained by device 2S is introduced by the running pass.The difference so-Ahl is formed in device 34 which provides the newapproximate sheet thickness s1 which is indicated in device 34a. Thevalue s1 is fed into line 17 and furnishes now `over the function device16 a new value Ks which is introduced into device 15 and after beingadded to the constantly received values Kv-l-Kt, of which K, changesconstantly under the influence of the running time factor, is addedthereto and provides an improved value Kw1. After repeating thecalculating processes in devices 14 and 12 an improved value A111 isobtained and over device 34 lan improved value s1, which in turn causesa new calculating operation through device 16, To the extent that thecalculating operations are constantly repeated in circuits 17, 16, 15,14, 12 and 34 a correct reduction Ahl is derived in a constantlyapproaching manner for the subsequent pass. From the differential device34 the reduction Ahl is fed to device 36 for the following pass. Thisvalue Ahl which changes mainly due to the influence of the constantlyrunning time factor determines in device 36 the number of therevolutions for the adjusting motor 37 which is `operated through switch38. The value A111 may change under the inuence of the running timefactor until starting the rolling of the work material in the reversepass, but thereafter is blocked in a manner not shown in detail. Theactual reduction A111 is equal to the adjusting value of the upperroller when Working always with the same rolling pressures since thereduction in the previous guide pass is determined with the frame underload so that the roller gap is eliminated. Due to the decreasing rollingpressure which takes place during this process a correction factor maybe determined in the adjusting device 36 in a known manner not shown indetail. This correction factor is comparatively the same as thedecreasing roller gap and corrects the `reduction A111 determined forthe following pass to a smaller adjustment than Ah1 Accordingly thedifference between two rolling pressures PWD-Pm from device 33 and thespring constant of the frame would :have to be introduced into theadjusting device 36.

In the case where the functions introd-uced into devices 16, 19, 21 and29 are correct the rolling pressure which was pre-selected at 33 must beshown -at the indicator instrument 39. If this is not the case thereason for this can be, aside from the exactness in collecting themeasurement values, only in that roller wear has occurred or that theroughness of the rollers is changing. As only small deviations areexpected in this respect it is possible to adjust during the rollingoperation the value for the roller diameter set at 13 also while thework material passes between the rollers in lorder to obtain thepre-selected rolling -pressure at 39. As the diameter of the rollers andtheir surface conditions changed only slowly such corrections will benecessary only from time to time. On the basis of test values one couldalso consider a change of the value in device 13 from pass to pass invery small magnitudes automatically.

During the second pass and after carrying out any necessary correctionsat device 13 the solenoid 23 is so actuated that switches 5, 9b, 24 and32 are closed while switch 6 `remains open. In this manner the runningpass is again a guide pass for a Subsequent third pass.

The operation described so far forms the basis for further automationespecially in View of the fact that the relationship between thepre-selected, decreasing rolling pressures and the consequentlydecreasing roller deflection depend up to an extended parallel conditionof the roller jacket lines in the rolling gap on the sheet width. Inthis respect it should ybe understood that with the same rollingpressure the rollers will exhibit la greater deflection the smaller thesheet width. In the case of a narrow sheet width the rolling pressureacts more as a point load and in the case of a Igreater sheet width moreas a stretch or area load. The goal should therefore be that after thefirst guide pass the last desired rolling pressure is determined inreference to the sheet width b which varies from sheet to sheet, underwhich pressure the Iroller deflection forms the smallest possiblegroove, thus rolling a finished sheet with optimum tolerance throughoutits width.

In reference to FIGURE 3 a control diagram is shown which is necessaryas a supplement to the diagram of FIGURE 2 when after a guide pass it isdesired to change to a determination of the reductions going backwardsfrom the last pass. The guide pass is still necessary in order to retainthe values of the sheet width, the temperature and the rolling speed,because the temperature and the rolling speed must be determined for thelast pass according to the novel process.

The control arrangement of FIGURE 3 corresponds 4to the devices ofFIGURE 2 with regard to the calculating devices 12, 14, 15, 1.6, 18, 19and 21. The starting point for the calculations are the values of theroller deliection Y which beginning at the last pass with the index nhave the smallest value and which are set in the example illustrated upto the fourth last pass by the index '71*3" at the devices 40-43.Depending on Whether the guide pass goes to the right or to the left thenumber n of the passes following the guide pass is also set in thedevice 44 so that the work material is rolled in the final pass to theexact point without requiring an empty pass. In setting the number ofpasses n in device 44 it is determined also how many of the devices40-43 are to furnish the values.

At the beginning the minimum roller deflection Yn is fed from the device40 into a function device 45 in which the rolling pressure is calculatedas function of the sheet width b, the roller diameter d and the rollerdeflection Y. The sheet width b is furnished by device 26 of thearrangement of FIGURE 2. The rolling pressure calculated for the lastypass is fed into calculator 14 into which the sheet width b is alsointroduced. The pressed length ld which is initially set at random isfed from the adjusting device 60 into device 14.

In the device 14 a Kw-value is derived which is fed into a differentialdevice 47 where it is compared with a KW- value derived from devices 15,16, 18, 19 and 21 in the manner described above in order to determinethe value for the nal pass n. The end temperature tn is set in device 48with a free selection and is fed into device 21 in order to determinethe existing deformation resistance Kt. Also the rolling speed must beset according to the number of passes bymeans of devices 49, 50, 51 and52. During the rst calculating process the value Vn `is taken fromdevice 49 and the pertaining Kv-value is calculated in device 19. Fromthe previously set desired value of the sheet thickness sn which comesinto device 46 through line S3 the Ks-value is calculated in device 16and fed to device 15.

In the case where the comparison of the Kw-values in device 47 producesa difference which deviates from zero an impulse is fed to the adjustingdevice 60 and changes the pre-selected value Id taken there at random ina direction corresponding to the sign of the deviation until throughdevice 14 a Kw-value is fed into the comparison device which is equal tothe value in the device 15. At the same time the value ld is fed intodevice 12 in which the reduction Abn of the last pass is calculatedwhich is fed into the device 62.

As soon as in device 47 the difference which is equal to zero is set, apulse is fed through line 55 to the adjusting device 41 for the rulerdeflection Yn 1 of the next -to the last pass in order to feed :now thisvalue for the following calculation to device 45. While this takes placethe value Yn from device 40 is cancelled. The pulse in line 55 whichinitiates the determination of the values for the next to the last passis also fed to the adjusting devices 49-52 in order to cancel the valuefrom 49 and to feed the value from 50` together with Vn 1 into device19. Furthermore adjusting devices 56, 57 and 58 are provided in front ofdevice 21 in which the temperature differences are pre-set from pass topass and in which during the second calculating process the temperaturetn l is taken from device 56. In order to consider the sheet thicknessduring the determination of Ks in the function device 16 the sum whichrepresents the next to the last sheet thickness .tn l is determined fromthe desired thickness sn in device 46 and the already determinedreduction Ahn in device 61. This value is fed to the device 16 duringthe second calculating process.

After determining the KW-value a zero difference cannot exist now incalculator 47 because the new rolling pressure calculated which pertainsto the next to the last pass is still coupled in device 14 with theprevious ld-value. The difference which is obtained again from device 47is conducted again over line 59 to device 60 in which the pressed lengthld is adjusted until the value fed into device 14 leads to a KW-valuewhich corresponds to the KW-value from devices 15, 18 and 21. With theadjustment of the value ld in device 60 the device 14 furnishes todevice 12 the ld-value which approaches a border value and from whichnow the reduction Ahn 1 of the next to the last pass is calculated andconducted to device 64.

As soon as any values are obtained in devices 64 or 63 the previouslyadjusted fixed values for the imaginary second to the last pass is takenoff in a conventional manner not described in detail by a feed backcoupling from devices 42, 57 and 51 with the index 1t-2. A new reductionAhn 2 is finally obtained at 66 and in device 65 a new sheet thickness s3. In a corresponding manner the reduction Ah 3 is obtained after afourth calculating process in device 68 and in device 67 the sheetthickness so' is derived before the fourth last pass.

In the case of an assumed pass number 11:4 the value so would have to beequal to the outlet thickness so of the running guide pass when thecourse of the Y-values which determine the rolling pressure has beencorrectly set over the four imaginary passes. In order to control thisso is compared in device 69 with the s,J value available from line 35.The difference is fed to a function device 70v into which variousfunctions of y depending on the number of passes are fed, as the fourlines in FIGURE 3 indicate. yn, which is the permissible deection of therollers in the last pass, must be constant as starting point. Dependingon whether the difference so-so is positive or negative a functiondifferent from the original function is set in the function device 70 bymeans of a signal from device 69. In the case where the originalfunction was set along line 71 and the difference .rd-so is positive thecalculated reductions are too large i.e. another function of y must beset which represents smaller deflection values for example the functionalong line 72. With these y-values the precalculation is repeated and incertain cases repeated several times until with a difference sO-so' iszero the correct function of y is set. The resulting values for therolling pressures Pv in device 45 represent then the correctlydecreasing rolling pressu-re for the adjusting device 33 shown in FIGURE2.

Into the function device 70 only functions of y between two bordervalues may be introduced as each course of y or PW must satisfy therequirement for a correct fiow adjusted rolling operation, In the casewhere a large difference so-so exists it is possible that from 69 noatter or no steeper course of y may be set over n, n-l, 11-2, n-3 atdevice 70. In that case the number of passes must be changed.

For this purpose a connection 74 is provided from the function device 70to the adjusting device 44 for the pass number n. Over this line thedifference .ro-s is conducted to 44 in case it is too large in order tobe able to adjust at 70 another one of the introduced functions of y. Iffor example at 70 the border value function according to line 73 is setand tvo-s0 is still positive it is possible to reduce the sum of thereductions Ah only by a reduction of the number of passes in order toobtain a smaller sa. This is obtained through device 44 yby means of asignal from device 70 when this device can no longer process a pulsewhich it has received.

In device 44 the pass number is adjusted appropriately by an evennumber, at least by 2, so as to avoid an empty pass. In the assumed casethe values at 42 and 43 and correspondingly at 57, 58 and at 51, 52would be cancelled. As the temperature of the guide pass is availablefrom device 27 in FIGURE 2 and since now only a temperature drop overtwo succeeding passes needs to -be considered the values at 48 and 56should be corrected simultaneously.

A new calculation with only two remaining passes will produce at 69 anegative difference so-so' as at 70 the function according to line 73 isstill set, and this difference causes at 70 a larger value yn 1 in thata function of y with a steeper characteristic is set until thedifference is equal to zero. The rolling pressures PW derived at 35 areconducted into the adjusting device 33 shown in FIGURE 2.

The device 70 changes thus within permissible limits ultimately therolling pressure course within a predetermined number of passes withoutdeviating from the principle of a correct flow adjusted rolling. Onlywhen the values conducted to device 70 are out of range for this devicethey are conducted into device 44 in order to change the pass number.

The values derived from the pre-calculation according to FIGURE 3 may beused in various ways for further rolling operations. First of all it ispossible to store from devices 62, 64, 66 and 68 the reductions indevice 36 of FIGURE 2 and to employ them before each reversing step ofthe rolling operation. But as indicated above the values PW for therolling pressure may be supplied from device 45 and fed according toneed to the adjusting device 33 of FIGURE 2. In this case the rollingmill is controlled, as stated at the start, over the rolling pressurecourse now determined with greater exactness, from device 33 whereineach pass may be again the guide pass for the following pass in order tocontrol the temperature continuously and so as to consider workstoppages.

It should also be pointed out that in the control arrangement accordingto predetermined rolling deflections according to FIGURE 3 the sheet endthickness sn is the basis for determining the existing deformationresistance Ks at 16 for the final pass because the determining initialthickness sn 1 is still not available.

From the resulting value sn sn 1 which provides too large a reductionAhn an sn 1 value is calculated at 61 from which an improved KS isobtained at 16 and over the zero-comparison at 47 etc., a Ahn valuewhich is again improved is obtained which, in a continuing approximationfinally provides the correct initial thickness sn 1 for the final pass.Only when the values at 62 or 61 have adjusted the predetermined valueswith the index n-l may be employed for the second calculating process.

The same applies to the prior passes because first the initial sheetthickness must be available with as much exactness as possible before acorrect Ks-value is available as basis for the calculation.

What is claimed is:

1. In a reversible rolling mill having at least one pair of opposedrollers for reducing the thickness of a metal sheet having a specificdeformation resistance which varies as a function of its temperatureduring a series of passes including at least a pair of passestherethrough, and means for varying the spacing of said rollers, theimprovement comprising: first means for generating a rst signalindicative of the reduction in thickness taking place as said sheet ispassing through said -rollers during the first of said pair of passes;second means for generating a second signal indicative of the width ofsaid sheet; third means for generating a third signal indicative of thepressure being exerted by said rollers on said sheet during said firstof said pair of passes; fourth means for generating from said first,said second, and said third signals, a fourth signal indicative of saidspecific deformation resistance of said sheet; fifth means forconducting said first, said second, and said third signals to saidfourth means; sixth means for selectively preventing said fifth meansfrom conducting said first and said third signals to said fourth means;said fourth means including means, operable when said sixth means ispreventing conduction of said first and said third signals to saidfourth means for generating a fth signal indicative of the continuouslychanging specific deformation resistance of said sheet; said fourthmeans further including means for generating from said fth signal, asixth signal indicative of a reduced roll spacing corresponding to adesired change in thickness of said plate during said second pass ofsaid at least one pair of passes which will produce a predetermineddesired pressure on said sheet in the second pass of said at least onepair of passes; sixth means responsive to said sixth signal for causingsaid means for varying the spacing of said rollers to move said rollersto said reduced spacing subsequent to said first pass and prior to saidsecond pass.

2. The improvement as defined in claim 1 wherein said first meansfurther includes means for generating a seventh signal indicative of thethickness of said sheet resulting from said first pass; and wherein saidfourth means further includes means for deriving an eighth signalindicative of the outlet thickness of said sheet which will result fromsaid reduced spacing during second pass, and means responsive to saidseventh signal for modifying said sixth signal to cause said sixthsignal to more accurately indicate the reduced roll spacingcorresponding to a desired change in thickness of said plate durin-gsaid second pass of said at least one pair of passes which will producea predetermined desired pressure on said sheet in the second pass ofsaid at least one pair of passes.

3. The improvement as defined in claim 1 wherein said means forgenerating said sixth signal generates a signal which produces a reducedroll pressure during said second pass of said at least one pair ofpasses.

4. The improvement as defined in claim 1 wherein said fourth meansfurther includes means for generating, from the known permissibledeflection of said rollers during the last pass of said series ofpasses, signals indicative of the desired rolling pressures for eachpass of said series of passes.

5. The improvement as defined in claim 4 wherein said fourth meansfurther includes means responsive to said signals indicative of thedesired rolling pressures for said series of passes for pre-calculatingthe required change in roller spacing for each pass of said series ofpasses.

6. The improvement as defined in claim 5 wherein said means forpre-calculating the lrequired change in roller spacing for each pass 0fsaid series of passes includes means for causing said pre-calculation tobe repeated with each pass of the series of passes while decreasing thenumber of passes in said series of passes.

7. The method of controlling screw settings in a reversible hot rollingmill for the flow adjusted level rolling of plates and sheets comprisingduring a first operating the steps of measuring during a guide pass therolling force, the inlet and outlet thickness, the speed and the widthof the work material, computing the parameters measured to develop underthe terms of a Vrolling formula a rst signal responsive to the partialspecific deformation resistance KW of the guide work material,developing a second signal resonsive to the partial specific deformationresistance KS in function of the actual thickness of the work material,developing a third signal responsive to the partial specific deformationresistance Kv in function of the actual speed Iof the work material,subtracting said second and third signal from said first signal toestablish a fourth signal responsive to the remaining partial speciedeformation resistance K1 being dependent on the actual work materialtemperature, eliminating from said fourth signal a fifth signal toresponsive to the actual temperature of the work material, andcomprising during a second operation the steps of switching off allmeasured values, storing the fifth signal to and the outlet thicknessvalue su, developing a fictive temperature t1 as sixth signal infunction of `the outlet thickness value so and the time lapse given bychronometer, developing a fictive value responsive to the partialspecific deformation resistance K1 as seventh signal, adding said secondand third signal to said seventh signal to produce a fictive valueresponsive to the specific deformation resistance Kw1, pre-setting arolling force value for the following pass less than the value measuredduring the guide pass, and computing said fictive, pre-set and storedparameters to establish under the terms of said rolling formula andoutput signal A111 responsive to the pass reduction for the lfollowingpass, each following pass serving as guide pass for the next pass.

8. The method according to claim 7, in which during the second operationa new pre-set speed value v1 is introduced to adapt said third signal tothe conditions of the following pass.

9. The method according to claim 7, in which during the the secondoperation a -fictive outlet thickness value S1 of the material to berolled in the following pass is developed from said outlet thicknessvalue So of the guide pass and the determined pass reduction value Al11for steady correction of said first signal, resulting in a correctedpass reduction value A111, this operation being terminated by switchingin all measured values with the beginning o-f the following pass.

10. The method according to claim 7, in which the rolling force to bepre-set during the second operation steps is scheduled for pass-bypassdecreasing rolling force.

11. The method of controlling screw settings in a reversible hot rollingmill for the ow adjusted level rolling of plates and sheets comprisingduring `a first operation the steps of measuring during a guide pass therolling force, the inlet Iand outlet thickness, the speed and the widthof the Work material, computing the parameters measured to develop underthe tenms of a rolling formula a first signal responsive to the specificdeformation resistance Kw of the guide work material, eliminating asecond signal responsive to the partial specific deformation resistanceK1 dependent on the actual work material temperature, and comprisingduring a second operation the steps of switching off all measuredvalues, steadily correcting said second signal K1 in function of thetime 4lapse given bya chronometer, reestablishing a fictive value Kw1 ofsaid first signal, pre-setting a rolling force Value for the followingpass, and computing said fictive preset values with stored measuredvalues to establish under the terms of said rolling formula an outputA111 responsive to the pass reduction for the 4following pass, eachfollowing pass serving as guide pass for the next pass.

12. The method according to claim :11, wherein during the secondoperation steps a rolling force schedule is established in advance for apre-set number of passes of a last pass series, comprising the steps ofpre-setting for each pass a roll deiiection value yn, yn 1, yn 2, yn3,from which values the last yn corresponds to the permissible andnecessary roll deflection during the final pass and the foregoing valuesare chosen in accordance with the desired flow adjusted level of rollingoperation, computing each deflection value to establish a correspondingrolling force schedule in function of said defiection values, themeasured width of the work material and the diameter of the rolls,simulating the rolling operation backwards from `the final pass and thedesired final thickness sn of the work material by adding the sum ofpass reduction values computed for each fictive pass under the terms `ofa rolling formula and said rolling force schedule to said desired finalthickness value sn, comparing this sum so with the measured outletthickness value so of the guide pass, repeating said simulatingoperation in the case a difference is obtained in said comparison.

13. The method according to claim 12, in that for each pass of thesimulated rolling operation a speed value and a temperature value ispreset and a ctive pass reduction v-alue Ahn, Ahn 1, Ahn1, Ahn 2, Ahn 3is computed to establish a rst signal responsive to the specificdeformation KW of the work material in function of the preset speed andtemperature values and the thickness values developed from the passreduction values for each fictive pass, said specific deformation valuesKW being compared with the corresponding values eliminated from thecomputing operation under the terms of a rolling formula, the

output of said comparison is made and held zero by varying a parameterld proportional to the computed pass reduction values.

References Cited by the Examiner UNITED STATES PATENTS 2,281,083 4/1942StOltZ 72-13 2,767,604 10/1956 Whalen 72-13 2,985,043 5/1961 Roberts72--13 3,111,946 11/1963 KOSS et al. 72-13 CHARLES W. LANHAM, PrimaryExaminer.

R. D. GREFE, Assistant Examiner.

1. IN A REVERSIBLE ROLLING MILL HAVING AT LEAST ONE PAIR OF OPPOSEDROLLERS FOR REDUCING THE THICKNESS OF A METAL SHEET HAVING A SPECIFICDEFORMATION RESISTANCE WHICH VARIES AS A FUNCTION OF ITS TEMPERATUREDURING A SERIES OF PASSES INCLUDING AT LEAST A PAIR OF PASSESTHERETHROUGH, AND MEANS FOR VARYING THE SPACING OF SAID ROLLERS, THEIMPROVEMENT COMPRISING: FIRST MEANS FOR GENERATING A FIRST SIGNALINDICATIVE OF THE REDUCTION IN THICKNESS TAKING PLACE AS SAID SHEET ISPASSING THROUGH SAID ROLLERS DURING THE FIRST OF SAID PAIR OF PASSES;SECOND MEANS FOR GENERATING A SECOND SIGNAL INDICATIVE OF THE WIDTH OFSAID SHEET; THIRD MEANS FOR GENERATING A THIRD SIGNAL INDICATIVE OF THEPRESSURE BEING EXERTED BY SAID ROLLERS ON SAID SHEET DURING SAID FIRSTOF SAID PAIR OF PASSES; FOURTH MEANS FOR GENERATING FROM SAID FIRST,SAID SECOND, AND SAID THIRD SIGNALS, A FOURTH SIGNAL INDICATIVE OF SAIDSPECIFIC DEFORMATION RESISTANCE OF SAID SHEET; FIFTH MEANS FORCONDUCTING SAID FIRST, SAID SECOND, AND SAID THIRD SIGNALS TO SAIDFOURTH MEANS; SIXTH MEANS FOR SELECTIVELY PREVENTING SAID FIFTH MEANSFROM CONDUCTING SAID FIRST AND SAID THIRD SIGNALS TO SAID FOURTH MEANS;SAID FOURTH MEANS INCLUDING MEANS, OPERABLE WHEN SAID SIXTH MEANS ISPREVENTING CONDUCTION OF SAID FIRST AND SAID THIRD SIGNALS TO SAIDFOURTH MEANS FOR GENERATING A FIFTH SIGNAL INDICATIVE OF THECONTINUOUSLY CHANGING SPECIFIC DEFORMATION RESISTANCE OF SAID SHEET;SAID FOURTH MEANS FURTHER INCLUDING MEANS FOR GENERATING FROM SAID FIFTHSIGNAL, A SIXTH SIGNAL INDICATIVE OF A REDUCED ROLL SPACINGCORRESPONDING TO A DESIRED CHANGE IN THICKNESS OF SAID PLATE DURING SAIDSECOND PASS OF SAID AT LEAST ONE PAIR OF PASSES WHICH WILL PRODUCE APREDETERMINED DESIRED PRESSURE ON SAID SHEET IN THE SECOND PASS OF SAIDAT LEAST ONE PAIR OF PASSES; SIXTH MEANS RESPONSIVE TO SAID SIXTH SIGNALFOR CAUSING SAID MEANS FOR VARYING THE SPACING OF SAID ROLLERS TO MOVESAID ROLLERS TO SAID REDUCED SPACING SUBSEQUENT TO SAID FIRST PASS ANDPRIOR TO SAID SECOND PASS.